Soil encompasses loose materials, which may include sand, silt, clay, organic matter, rocks and minerals of various sizes, gravel, humus, volcanic ash, regolith, and mixtures thereof. Soil is found on the Earth and may also be used as growth media in above-ground planting beds or other containers of various sizes (e.g., in a greenhouse). Soil also contains gases in the voids between the loose materials. Soil may also contain relatively large amounts of water by volume. Damp soil can be about 40% water by volume and even seemingly dry soil can be about 15% water by volume.